prompt

First recorded in 1400–50; (adjective) Middle English prompte “ready, eager,” from Old French pront, prompt and Latin promptus “manifest, at hand, ready, quick, prepared,” special use of past participle of prōmere “to bring forth or out, set forth (an idea), deliver (a speech), publish (a book),” equivalent to the prefix prō- “advancing or projecting forward” + (e)mere “to take, buy”; (verb) late Middle English prompten, from the adjective or possibly from unattested Medieval Latin promptāre “to incite, induce,” from Latin promptāre “to distribute in abundance, be steward of,” a frequentative of prōmere; see pro-¹

Prompt, adjective and verb, presents some oddities. One is that the first recorded date for the adjective is about 1425 and for the verb, 1428, making it impossible to determine which part of speech was the source for the other. A second oddity is that prompting, the gerund (verbal noun) logically derived from prompt and meaning “incitement or impulse to action,” is first recorded in 1402, a quarter of a century before the verb. A third difficulty is that the Medieval Latin verb promptāre, the possible source of the English word, does not exist per se but is inferred from its Medieval Latin derivative noun promptātor “one who incites or urges,” recorded in the mid-15th century, and the Old Italian verb prontare “to urge, press.”
The commercial sense of the noun prompt “a time limit given for payment for merchandise purchased" dates from the mid-18th century. The computer sense of the noun “a message or symbol on a display screen requesting more information from a user" dates from 1977.